According to the Library of Congress, no U.S. senator in history has defeated more sitting Republican members of the Congress than Democrat Tom Harkin of Iowa.

He has five tusks on his wall.

Harkin's office confirmed that little nugget the other day, and it raises an interesting question: Who will the Republicans offer as the sacrificial elephant in 2008?

The senator's up for re-election then. With all the current hullabaloo over the governor's race, legislative contests, early presidential campaigns, battles for Congress and the political fallout over CIETC, we've almost overlooked that fact that our junior senator is up for a contract renewal in two years.

Yet so far, no big-name Republicans seem to be making the moves needed to challenge him. Only obscure names are heard. Could the ghosts of Bill Scherle (1974), Roger Jepsen (1984), Tom Tauke (1990), Jim Lightfoot (1996) and Greg Ganske (2002) be scaring off credible GOP challengers?

Could 2008 be the year that Harkin, finally, gets the same sort of free ride from Republicans that Democrats have been giving Chuck Grassley for 20 years?